Laminate Effectiveness

[Chet]

  Has anyone done a test of the improvement in performance of a PMG with laminates, vs. without? I mean, tested an air-core unit, added laminates and tested again, to see the actual numbers?

Chet

[scoraigwind]

Efficiency is not a fixed number - it depends on conditions.

At low power when the machine cuts in you will get losses in the laminations that will make it less efficient than the air cored double rotor units.  However the laminations do increase the flux in the stator and so allow a unit of the same size to produce a higher maximum output with good efficiency.

For me the low windspeeds are the times when I am needing the most power I can get, so I like to have a machine that is efficient in low winds.  In higher winds there is usually plenty of power to spare so I don't care too much if the efficiency is lower then nor whether I can produce a very high power output that I do not need.

There is no doubt you can achieve a higher power density using laminations and get more out of a given set of magnets that way but I dislike the starting problems and the construction hassles invovled in laminated cores so I avoid them now.  

I also like the way that the air core machines do not have so much self inductance, so the output current doesn't roll off like it does in the laminated cores.  Most laminated machines have a maximum current that you cannot exceed and they just go faster and faster if you try.

So it's not a simple comparison, but each has its own merits.

[Hank]

Yes I have, there is a definate improvement.

Go to this previous posting by me.

http://www.fieldlines.com/story/2004/3/21/17235/6660

Going dual rotor is a bit better and as Hugh stated there is less magnetic friction therefore the PMG will start up quicker in low winds.

I've made both type of units and my opinion is that the dual rotor type is much better.

Have fun,

Hank

[windstuffnow]

  I've been building slotted silicon laminant stators for quite some time.  Just reciently built one of hughs dual rotor versions.  I would say the dual rotor produces about 1/2 of that of a silicon stator given the same dimension, wire, magnets and turns.( although only one set of magnets are needed )  

  The ease of building the dual rotor stator is less labor intensive and probably a little less expensive but the cost in magnets doubles which makes up for any savings.  Like anything else each design has its pro's and con's and depends considerably on its application.

Have Fun

Windstuff Ed